Derivatives and Risk Management Derivatives and Risk Management - Offsetting Assets and Liabilities (Details) - USD ($) $ in Millions	Jun. 30, 2017	Dec. 31, 2016
Derivative
Net derivative contracts, hedge derivatives, net	$ (214)	$ (291)
Prepaid Expenses and Other
Derivative
Net derivative contracts, assets	7	31
Other Noncurrent Assets
Derivative
Net derivative contracts, assets	1	6
Other Accrued Liabilities
Derivative
Net derivative contracts, liabilities	(216)	(326)
Other Noncurrent Liabilities
Derivative
Net derivative contracts, liabilities	$ (6)	$ (2)